Expansion screw structure

Abstract

An expansion screw structure contains an anchor for mating with a screw. The anchor includes a first segment and a second segment which have a central axis, and a shank. The anchor further includes a head which has a slot. The shank includes a first threaded section, multiple cutouts, a decreasingly conical tip, a second threaded section, a slit, a first support foot, a second support foot. The slit has a first part, a second part, and a third part. The second part has a first raised portion, the second part has a second raised portion, and the third part has a connection section and a thin coupling strap. The thin coupling strap has a first thickness, the connection section has a second thickness, and the first thickness of the coupling strap is ⅓ of the second thickness of the connection section.

What is claimed is: 
     
       1. An expansion screw structure comprising:
 an anchor for mating with a screw; 
 wherein the anchor includes a first segment and a second segment opposite to the first segment, the first segment and the second segment have a central axis, and a shank extends from the first segment to the second segment, 
 wherein the anchor further includes a head formed on the shank at a top portion of the first segment, and a diameter of the head is more than a diameter of the shank, and the head has a slot defined in a top surface therein so as to accommodate a tool or the screw, 
 wherein the shank includes a first threaded section formed on an outer wall of the shank and extending from the first segment to the second segment, the first threaded section is in a positive thread type, and the shank includes multiple cutouts defined on the outer wall thereof adjacent to the second segment, 
 wherein the second segment of the shank has a decreasingly conical tip, the decreasingly conical tip has a second threaded section formed on an outer wall thereof, 
 wherein the shank includes a slit formed thereon and communicating with the slot so that the shank has a first support foot and a second support foot separated from the first support foot by the slit, the slit extends from a top of the shank to a bottom of the shank, and the slit has a first part, a second part, and a third part, wherein the first part is close to the first segment and passes through the central axis, the second part is connected with the first part and bends so that the second part has a first raised portion opposite to the first support foot, and the second part has a second raised portion opposite to the second support foot, the third part is connected with the second part and obliquely extends to the second support foot so that a length of the first support foot is not equal to the second support foot, the third part has a connection section arranged on a distal end thereof and configured to connect the first support foot and the second support foot, the third part has a thin coupling strap configured to connect the first support foot and the second support foot, wherein the thin coupling strap has a first thickness, the connection section has a second thickness, and the first thickness of the coupling strap is ⅓ of the second thickness of the connection section, the first thickness is not more than 3 mm. 
 
     
     
       2. The anchor as claimed in  claim 1 , wherein the first threaded section has multiple deep threads adjacent to the first segment, and the first threaded section has multiple shallow threads proximate to the second segment, wherein a depth of the multiple deep threads is more than the multiple shallow threads, and the multiple cutouts are located on a same zone as the multiple shallow threads. 
     
     
       3. The anchor as claimed in  claim 1 , wherein the second threaded section is in a reverse thread type and intersects with the multiple shallow threads of the first threaded section. 
     
     
       4. The anchor as claimed in  claim 1 , wherein the first support foot has a first curved groove formed on an outer wall thereof adjacent to the head, and the second support foot has a second curved groove formed on an outer wall thereof proximate to the head. 
     
     
       5. An expansion screw structure comprising: an anchor for mating with a screw;
 wherein the anchor includes a first segment and a second segment opposite to the first segment, the first segment and the second segment have a central axis, and a shank extends from the first segment to the second segment, wherein the anchor further includes a head formed on the shank and the first segment, and a diameter of the head is more than a diameter of the shank and the head has a slot defined therein so as to accommodate a tool or the screw, wherein the shank includes a threaded section formed on an outer wall of the shank and extending from the first segment to the second segment, wherein the second segment of the shank has a decreasingly conical tip, wherein the shank includes a slit formed thereon and communicating with the slot so that the shank has a first support foot and a second support foot separated from the first support foot by the slit, the slit extends from a top of the shank to a bottom of the shank, and the slit has a first part, a second part, and a third part, wherein the first part is close to the first segment and passes through the central axis, the second part is connected with the first part and bends so that the second part has a first raised portion opposite to the first support foot, and the second part has a second raised portion opposite to the second support foot, the third part is connected with the second part and obliquely extends to the second support foot so that a length of the first support foot is not equal to the second support foot, the third part has a connection section arranged on a distal end thereof and configured to connect the first support foot and the second support foot, the third part has a thin coupling strap configured to connect the first support foot and the second support foot, wherein the thin coupling strap has a first thickness, the connection section has a second thickness, and the first thickness of the coupling strap is ⅓ of the second thickness of the connection section, the first thickness is not more than 3 mm. 
 
     
     
       6. The anchor as claimed in  claim 5 , wherein the shank includes multiple cutouts defined on the outer wall thereof adjacent to the second segment, and wherein the decreasingly conical tip has a threaded section formed on an outer wall thereof. 
     
     
       7. The anchor as claimed in  claim 5 , wherein the threaded section has a first threaded section and a second threaded section, the first threaded section has multiple deep threads adjacent to the first segment, and the second threaded section has multiple shallow threads proximate to the second segment, wherein a depth of the multiple deep threads is more than a depth of the multiple shallow threads. 
     
     
       8. The anchor as claimed in  claim 7 , wherein the second threaded section is in a reverse thread type. 
     
     
       9. The anchor as claimed in  claim 5 , wherein the first support foot has a first curved groove formed on an outer wall thereof adjacent to the head, and the second support foot has a second curved groove formed on an outer wall thereof proximate to the head. 
     
     
       10. The anchor as claimed in  claim 5 , wherein a first thickness is within 0.4 mm to 1.2 mm.